The graphic arts industry is aware of the concern for handling a stream of sheets moving from a printing press and going to a sheet stacker where the sheets are collected in a stacked form. This is usually accomplished in continuous movement of the sheets. For instance, U.S. Pat. No. 3,781,005 shows a continuous stream of sheets moved on conveyor belts and into a collected stack. In this regard, it is sometimes desirable that the stream be somehow interrupted so that the sheets forming the stack can be clearly segregated from the remainder of the sheets which are still in the stream. Still further, it is sometimes desirable that the sheets formed in a stack are placed therein in an accurate count.
With regard to interrupting or forming a gap in the stream of sheets, U.S. Pat. No. 3,834,288 shows one method of restricting or actually stopping the sheets in their path in the stream, so that the sheets that are upstream from the point of stopping or interruption are actually collected or bunched together so that those sheets in the downstream position can continue on into the stack by themselves. However, in that arrangement, there must be provision for bunching the sheets in the stream, and this frequently involves concern with respect to keeping the sheets in a neatly aligned relationship, since the interruption of the stream flow, or the bunching mentioned, will inherently cause the sheets to get out of alignment and thus create a problem with respect to desired neat stacking.
Accordingly, the present invention provides a method and means for forming a gap in a stream of sheets, and to do so in a manner whereby the sheets are still continuously moved toward the stacker at a desired previous and uniform rate of movement, and there is no bunching of the sheets in the stream in order to form the gap. Still further, the sheets can be accurately counted, with respect to the location of the gap, and thus an accurate number of sheets can pass on to the collected stack of sheets.
Still further, the present invention accomplishes the foregoing, and distinguishes over the prior art, as mentioned, and does so in a facile and inexpensive manner so that the method and apparatus are extremely practical for commercial installation and are highly reliable in forming the accurate count of sheets and in providing a distinct gap in the sheets, without upsetting the continuous flow of sheets to the stack and without getting the sheets out of alignment, all so that they are neatly stacked in the stacker. Thus, a constant stream condition is maintained, rather than the bunched gap condition as commonly used in the prior art.